The instant invention relates to a full mold casting process in which a complete positive model, made of a thermally decomposable material, is placed into a molding box filled with sand. The sand is compacted by tamping it in, and the casting metal is poured on the thermally decomposable model. The model is decomposed by the casting heat. The invention includes a device for carrying out the process.
To produce castings, molds consisting of two halves are generally used. However, this division of the molds is only possible within certain dimensional tolerances, and as a consequence, defects may occur within the mold joint due to offset burrs, sand washouts, metal penetrating into the sand mold, charred portions of sand, and the like. All these defects appear on the cast and must be eliminated by grinding, stripping, knocking, sawing, or the like.
To avoid these extensive manual tasks a model is placed into a molding box with loose, dry sand in the so-called full mold casting process. To be able to remove the model, the model is made of a thermally decomposable material so that the model is decomposed by the casting heat. When an undivided model is used, a casting without burrs is produced.
It has been found, however, that not all types of models can be molded in this manner and it is especially difficult to satisfactorily embed moldings with dome-shaped cavities, such as pump housings and similar shapes, in the sand because the sand does not rise to fill these cavities. It is, therefore, a disadvantage of this known full mold casting process that such moldings cannot be molded and cast in this process but must be produced with batch cores or in the conventional molding process, in several parts. All molds in which the sand would have to rise into such cavities as well as into communicating pipes are, therefore, unusable with the known full mold casting process.